Title

High-Pressure Near-Infrared Raman Spectroscopy Of Bacteriorhodopsin Light To Dark Adaptation

Abstract

Near-infrared (NIR) Raman spectroscopy is employed as an in situ probe of the chromophore conformation to study the light to dark-adaptation process in bacteriorhodopsin (bR) at variable pressure and temperature in the absence of undesired photoreactions. In dark-adapted bR deconvolution of the ethylenic mode into bands assigned to the all-trans (1526 cm-1) and 13-cis (1534 cm-1) isomers yields a 13-cis to all-trans ratio equal to 1 at ambient pressure (Schulte et al., 1995, Appl. Spectrosc. 49:80–83). Detailed spectroscopic evidence is presented that at high pressure the equilibrium is shifted toward the 13-cis isomers and that the light to dark adaptation kinetics is accelerated. The change in isomeric composition with temperature and pressure as well as the kinetics support a two-state model activation volumes of -16 ml/mol for the transition of 13-cis to all-trans and -22 ml/mol for the reverse process. These compare with a conformational volume difference of 6.6 ml/mol, which may be attributed to the ionization of one or two residues or the formation of three hydrogen bonds. © 1995, The Biophysical Society. All rights reserved.

Publication Date

1-1-1995

Publication Title

Biophysical Journal

Volume

69

Issue

4

Number of Pages

1554-1562

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1016/S0006-3495(95)80027-5

Socpus ID

0028980597 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/0028980597

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